1. Technical Field
The present disclosure relates to an information recording medium, an information recording method, an information recording device, an information playback method, and an information playback device for being able to efficiently ensure and use a management information area necessary to record and play back data in and from an information recording medium including a plurality of information recording surfaces in each of which information is optically recordable in a land and a groove, shortening a time necessary for processing of acquiring or recording management information, and being able to perform recording or playback without being influenced by a transmittance change due to a recording state or a recording state of an adjacent track.
2. Description of the Related Art
Nowadays, various optical discs such as a DVD (Digital Versatile Disc) and a Blu-ray (registered trademark) disc (hereinafter, referred to as a BD) are used as the information recording medium in which a picture or data is stored. Because the optical discs have storage reliability higher than that of a Hard disc Drive (HDD) or a magnetic tape, uses of the optical discs are currently extended from a conventional use of the recording of AV data such as audio and video to long-term storage of the data, namely, a data archive use.
However, the optical disc has a data storage capacity per volume about one third the HDD or magnetic tape. Therefore, from the viewpoint of space efficiency of the optical disc during the storage, there is a demand for technological development of improving the data storage capacity per volume without increasing cost.
Recently, a BDXL having recording density of about 33.4 GB per layer is available as the optical disc having the highest volume recording density in the BD. The BDXL has storage reliability of at least 50 years, and has reliability ten times the HDD having the storage reliability of about 5 years from the viewpoint of long-term data storage. Therefore, the archive data currently stored in the HDD is stored in the optical disc, which allows the long-term storage reliability to be compatible with the storage cost.
From the viewpoint of power consumption, compared with the HDD that consumes power during the data storage, the optical disc does not consume the power during the data storage, but an emission amount of carbon dioxide can be reduced as a green storage considering an earth environment. Nowadays, an increase in power consumption becomes a large problem in a large-scale IT (Information Technology) system such as a data center. The power consumption can be reduced when the optical disc is used as the archive data storage.
In the data center, because of a high requirement for a storage space, there is a demand for further improving the recording density per volume in order to use the optical disc in the archive data storage.
Examples of the technology of improving the recording density per volume of the optical disc include a land-groove recording and playback technology of improving the track recording density and a multi-layer technology including a plurality of recording layers in each of which data is recorded.
The land-groove recording and playback technology is a technology used in a DVD-RAM, and the data recorded in only the land or groove of the optical disc is recorded in both the groove and the lands to improve the track recording density. Usually, when the track recording density of the optical disc is improved, because tracing control is performed on the groove of the track with a light beam, necessary light deflected from the groove decreases, and the track cannot be traced with the light beam.
Assuming that λ is a wavelength of a laser beam used as the light beam with which the optical disc is irradiated, and that NA is a numerical aperture of a lens that forms the light beam, a limit gap between the lands or grooves, namely, limit track pitch L is given by as follows.L=(λ/NA)×0.6
When the track pitch is smaller than limit track pitch L, the light deflected from the groove cannot be detected, and the track tracing control cannot be performed. For example, limit track pitch L becomes 650 nm in the DVD having NA of 0.6 and λ of 650 nm.
In the DVD-RAM, the data is recorded in both the land and the groove to obtain the track pitch of 615 nm, thereby improving track density (refer to Unexamined Japanese Patent Publication No. 7-29185, for example).
In the multi-layer technology including the plurality of recording layers in each of which the data is recorded, the plurality of recording layers made of a material in which the data is recorded are included in one optical disc (refer to PTL 2: Unexamined Japanese Patent Publication No. 2010-97685, for example). The BD including two recording layers and the BDXL including three or four recording layers are already commercialized as the practical optical disc.
However, when the number of recording layers increases, the light transmittance or reflectance changes due to the recording state, which results in a problem in that it is difficult to ensure recording quality satisfying the long-term data storage reliability.
There is currently performed the technological development of improving the recording density per volume in the optical disc such that the data is recorded in both the land and the groove while the track pitch is further narrowed compared with the BD and the BDXL. According to the technological development, in one side of one optical disc, it is said that the capacity of one layer is larger than or equal to 50 GB, and that the capacity of three layers exceeds 150 GB.
At this point, information about a defect generated on a recording surface by dust or a scratch and management information of information about the recording state on the optical disc are required to perform the recording or playback of the optical disc. Particularly, a write-once type optical disc in which the information can be recorded only once includes a tentative management information area where the management information is transiently updated, and the latest management information is additionally updated in the tentative management information area (refer to Unexamined Japanese Patent Publication No. 2005-56542, for example).
As the recording density of the optical disc increases, a size of the management information increases, and the number of update times of the management information also increases. Therefore, there is a demand for enlarging the size of the area where the management information is tentatively recorded. A method for ensuring the management information area in a lead-in area that a user cannot access is generally adopted as a method for ensuring the large management information area. Additionally, there is a method for separately ensuring the management information area at both ends of data area similarly to a later-described spare area ensured to alternate the defect (refer to Unexamined Japanese Patent Publication No. 2005-276433, for example).